The present invention relates to a wrapping wheel of a cigarette packing machine.
In the tobacco industry, a continuous cigarette packing machine is known, which comprises a wrapping wheel mounted to rotate continuously about a respective axis of rotation, and in turn comprising at least one seat for a respective group of cigarettes enclosed in a respective tubular wrapping oriented with its longitudinal axis parallel to the axis of rotation of the wrapping wheel. The tubular wrapping normally has two tubular end portions, each projecting axially beyond a respective end surface of the group of cigarettes, and each comprising two parallel walls.
As the wrapping wheel rotates continuously, each end surface of the group of cigarettes is conveyed at a given speed and in a given traveling direction along a respective annular path, which extends crosswise to said two walls of the respective tubular end portion of the tubular wrapping and in a respective plane about the axis of rotation of the wrapping wheel. In the course of the above movement, folding devices engage and fold said two walls of each tubular portion onto the relative end surface of the group of cigarettes.
Said folding devices normally comprise, for each seat on the wrapping wheel, a movable folding device supported by the wrapping wheel and for folding, of said two walls, the one located at the rear in the traveling direction; and a fixed folding device supported by the packing machine in a fixed position along the path of the seats, and for folding, of said two walls, the one located at the front in the traveling direction of the seats.
Known folding devices of the type described above are not normally suitable for use over a given maximum operating speed, above which, the impact of the tubular wrapping, and in particular of said front wall, against the fixed folding device may easily result in tearing of the tubular wrapping.
One possible solution to the problem is to fit the wrapping wheel, for each seat, with a movable folding device for the rear wall, and a further movable folding device for the front wall.
Such a wrapping wheel, however, is relatively complicated and expensive, on account of the relatively complex movements performed by the movable folding devices, and which therefore call for relatively expensive, normally cam-type, actuating devices.
It is an object of the present invention to provide a wrapping wheel designed to eliminate the aforementioned drawbacks.
According to the present invention, there is provided a wrapping wheel of a cigarette packing machine, the wrapping wheel having a first axis of rotation and comprising at least one seat for a respective group of cigarettes enclosed in a respective tubular wrapping oriented with a respective longitudinal second axis parallel to said first axis and having at least one tubular end portion, which projects axially beyond a respective end surface of said group and comprises two parallel walls; and folding means for folding said two walls of said tubular end portion onto the relative said end surface; said wrapping wheel being mounted to rotate about said first axis to move each said end surface at a first speed and in a given first direction along a relative annular first path crosswise to said two walls and extending in a relative plane about the first axis; and being characterized in that said folding means comprise at least one folding device, which has an outer surface tangent to a relative said first path and comprises at least one folding member, and actuating means for moving the folding member in a given second direction along an annular second path, a projection of which in the relative said plane comprises a portion substantially coincident with a portion of the first path.